Sewing machine



Dec. 29, 1936.

H. F. BRIGGS ET AL SEWING MACHINE Filed Sept. 14, 17933 3' Sheets-Sheetl ATTORNEY 193 H. F. BRIGG ET AL ,0 3

SEWING MACHINE .Filed Sept. 14,1955 .3 Sheets$heet 2 ATTORNEY Dec. 29,1936. H. F. BRIGGS. ET AL 2,

SEWING MACHINE Filed $ept. 14, 1933 s Sheets-Sheet s 2J0" w w" M,

@TORNEY 2 Patented Dec. 29, 1936 2 335 UNITED PATENT OFFICE SEWINGMACHINE Howland F. Briggs, Buffalo, and Robert N. Cundall, Lackawanna,N. Y., assignors to Consolidated Packaging Machinery Corporation,Buffalo, N. Y., a corporation of New York Application September 14,1933, Serial No. 689,400

3 Claims. (01. 112--215) Our invention relates to sewing machines,paremployed in connection with driving mechanism ticularly sewingmachines such as are adapted for comprising a main drive shaft extendingparallel heavy duty. The primary purpose for which to the principal axisof the needle and having these heavy duty sewing machines are designedeccentric means mounted thereon for the pur- 5 is the sewing of heavymulti-ply paper bags such pose of driving the feeding mechanism as wellas 5 as are used for packaging cement and similar maother moving partsof the machine, and the sewterials. These bags frequently consist offour or ing machine of our invention is also especially five plies ofheavy kraft paper and are often adapted to be employed in conjunctionwith gusseted so that the needle must traverse as mechanisms for fillingand closing open-mouth many as twenty plies of paper. The weight of bagsas those described and claimed in the 00- 10 such a package isfrequently very great so that pending application of Robert N. Cundall,Serial a sturdy machine is necessary to close their open No. 640,758,filed Nov. 2, 1932, and the copending mouths. applications of Robert N.Cundall and Lincoln A.

We have found that previous sewing machines Cundall, Serial Nos. 666,114and 686,816, filed operated satisfactorily on cloth bags even with April19, 1933 and September 9, 1933, respectively. 15

slight inaccuracies of feeding movement, because With respect to thisand other apparatus, it is of the relatively flexible character ofcloth, wheredesired to point out that, while the feeding mechas if suchinaccuracies were allowed in the closing anism is referred to herein asbeing for the purof filled paper bags the defective and irregular poseof advancing the material through the sewstitching produced would notefficiently close the ing machine, it is not absolutely essential thatbag and would often result in breaking or jamthe actual forward motionof the material be ming the mechanism. An object of our invention causedby the feeding mechanism, as this motion is to devise a machinesumciently strong and may be effected by other means and the feedingrugged to operate on heavy filled paper bags. mechanism may actuallycause the sewing ma- A specific feature of our invention comprises achine to travel along the paper, whether the latter 25 feed dog somounted and operated as to have is stationary or in motion. In anyevent, howconstant' positive backing rather than the old ever, thefunction of the feeding mechanism is to style of mounting of the feeddog at the. end of assist in producing a relative movement of therelatively long members. These long members material being sewn withrespect to the sewing 3 could not stand the severe stresses withoutbendmachine, and it is immaterial in so far as our ing, and no operatingmechanisms were found present invention is concerned whether the onewhich could operate through short members due or the other is actuallycaused to move by the to the relative lack of space in the normal sewingfeeding mechanism.

head. Our invention is designed to overcome this Thus, in sewing themouths of previously filled problem. bags, especially bags adapted tocontain large A further object of our invention is to provide amounts ofmaterials, it is not ordinarily feasible -a feed dog which operates in astraight path durto move the bags along in an intermittent jerking thefeeding movement so that the stitches will ing movement, and therelatively stiff and rigid have exactly the same length, an end whichcould paper allows for no movement of the paper rel-a- 40 ot be atta in& Sewing mechanism v n a tive to the head while the needle is engagedwith 40 feed dog designed to operate in a rounded path the paper duringstitching.

during its feeding stroke since the smooth, hard As shown in theaforesaid co-pending applicasurface of the paper would not allow such afeed tions of Robert N. Cundall and Lincoln A. Cundall,

dog to positively feed during the time when it was a sewing head forsuch use may be pivotally approaching and receding from the presserfoo-t. mounted on an axis normal to the plane of the A further object ofour invention is to provide material being sewn, the head being rockedabout a feed dog, having the foregoing characteristics this axis as thepaper advances, or as the head and advantages, which approaches andrecedes is moved along the paper, as the case may be. from the plane ofthe material in substantially a Our invention is therefore especiallyadapted.

normal path thereto, and without lateral devito be employed in a sewinghead of this character, 50 ation from the line of stitching, therebyavoiding in which the various moving parts are driven the gouging andmarking of the material which from a main drive shaft having its axisparallel unavoidably occurs in the use of feed dogs pivoted to that ofthe needle and having eccentric means on relatively long structuralmembers. for actuating the needle, the feeding mechanism Such mechanismis especially adapted to be and the looper mechanism. Such a head, when55 tially or entirely in the line of thrust.

employed for stitching the mouths of previously filled bags, and, it maybe, for other purposes as well, is preferably pivotally mounted on anaxis passing through the center of gravity of the head or coaxial withthe drive shaft, but in any event normal to the plane of the materialbeing sewn.

More specifically, our invention contemplates, in addition to a feed dogmechanism mounted upon a shaft in the manner aforesaid extendingparallel to the direction of advancement of the material being sewnthrough the machine, .the provision of means, actuated by an eccentricl'ocatecl upon or driven by the main drive shaft, for reciprocating thefeed dog mechanism to and fro along this shaft, that is to say, in thedirection of motion of material being sewn and opposite thereto; and ofmeans, also driven by an eccentric device mounted upon the main driveshaft or connected thereto, for contributing a reciprocal movement tothe feed dog mechanism about the principal axis of the aforesaid shaftextending parallel to the direction of the movement of the materialbeing sewn, and whereby the feed dog proper is caused to advance throughthe feed plate to grip the material and to be withdrawn therefrom. Thelatter means is furthermore so designed and constructed in accordancewith our invention that the thrust exerted by the presser foot or thefeasible biasing means therefor, through the presser foot and thematerial being sewn upon the feed dog and tending to force the latterback through the feed plate, is resisted by structural members lyingsubstan- In other words, the feed dogis provided with a rigid metalbacking located directly in the line of thrust exerted by the presserfoot, as distinguished from prior devices in which this thrust wasresisted by flexible means or by structural members extending more orless laterally with respect to the line of thrust and supported at apoint removed from the direct line of thrust.

Thus, insome prior devices of the general character recited hereinabove,the feed dog mechanism has been mounted at the end of a relatively longstructural member extending laterally with respect to the line of thrustof the presser foot and supported at some distance therefrom, andv whensuch prior devices were adjusted to give a sufficiently strong grippingof the material being sewn to take care of such stresses as are involvedin sewing the mouths of large open-mouth filled paper bagsor the like,such vlateral members tended to yield or bend, thereby reducing the gripof the feed dog or presser foot on the material being sewn or causing amisalignment of the material being sewn during the operation.

According to our invention, however, this disadvantage of prior devicesis'overcome by means of the device herein set forth and the machine maybe adjusted to grip the material being'sewn very tightly withoutfear ofbending or'overstressing any structural parts thereof, or of injury tothe mechanism, or of a tendency toward misalignment of material beingsewn as it is advanced through the machine.

In a more specific aspect, our invention contemplates the provision of acam device, preferably a sliding cam, adapted to travel between the feeddog mechanism; and a fixed member, for example, the frame of the sewingmachine itself, in such manneras to'produce an oscillation or reciprocalmotion of the feed-dog device about the shaft on which it is mounted,the insertion or operation of the cam mechanism with respect to the feeddog mechanism taking place substantially in the line of thrust exertedby the presser foot and providing structural means in which the thrustof the presser foot produces a compressive stress in the feed-dogbacking means as distinguished from bending moment or shear.

In another more specific aspect ,ourinvention contemplates the provisionin a sewing machine, of a single main driving shaft, a needle barreciprocating in a line parallel to the main shaft, a looper cooperatingtherewith to form stitches, a feed dog for advancing the materialrelatively to. the needle, and eccentrics on the mainshaft for operatingthe needle, the looper and the feed dog. The latter provision is atremendous ad- Vance in that it makes practical the extremesimplification and efiicient operation of sewing mabe adjusted and onceits correct contour is lost must be replaced, These cams were veryexpen:

sive due to the accuracy necessary, and required. the maintenance ofexpensive routing or special milling machines at the manufacturer's,plant,

With our invention each rotating driving element comprises a simpleeccentric, easily turned out on a lathe and easily adjustable tocompensate.

for wear as is well known. Further, our invention comprises other simpleparts in all respects, any of which may be economically and easilyreplaced.

In order that our invention may be more clear- 1y set forth andunderstood, we now describe,.

with reference to the drawings accompanying and forming a part of thisspecification, an illus trative instance of the manner and form in whichour invention may be embodied and utilized. In.

these drawings:

Such cams, subject- Fig. 1 is an elevational view of a sewing machineconstructed. in accordance with our present invention, in which thesewing machine appears with the usual cover plate, as 'well as otherparts having no bearing upon the present invention, removed for the sakeof clarity to give a better view of the operating andstructural parts ofthe machine;

Fig. 2 is a bottom view of the apparatus illustrated in Fig. 1;

Fig. 3 is an enlarged vertical sectional view of a portion of theapparatus illustrated in Fig. .1 taken on the line 33 of Fig. 1;

Fig. 4 is an enlarged vertical sectional view of the apparatusillustrated in Fig. 3 along the line 44 of Fig. 1;

Fig. 5 is an enlarged vertical sectional view similar to Fig. 1, buthaving parts of the casing broken away to allow a clear view of the feeddog, and the looper mechanism removed in part to allow a clear view ofthe feed dog operating means;

Fig. 6 is a schematic view of the path of travel of the feed dog, theline AB representing the face plate of the machine, and the shadedportion representing the feeding stroke and illustrating the straightline characteristics thereof;

Fig. '7 isa similar schematic view representing the movement of theneedle point normalto the material and illustrating its timed relationto th feed dog travel;

Fig. 8 is a similar schematic view representing the orbital pathofmovement of a point on the looper in relation to the needle whichreciprocates normal to the plane of Fig. 8;

Fig. 9 is a View similar to Fig. 6 but represent ing a feed dog pathresulting from a simple variation which allows a shorter feeding stroke;

Fig. 10 is a view similar to Fig. 6 but representing a feeddog pathresulting from a simple adjustment which also allows a shorter feedingstroke and hence allowing a relatively greater time for the needle andlooper to operate; and

Fig. 11 is a cross section taken on line i l--l l of Figure 2 of themeans to cause the feed dog to move vertically,

Similar reference numerals designate similar parts in each of theseveral views of the drawings.

Referring now to the drawings, there is illustrated a sewing machine orsewing head having a frame I of more or less conventional shape with athroat portion 2 through which the material to be sewn is advanced. Thedirection of advancement of material through the sewing head, as viewedin Fig. l is perpendicular to the plane of illustration and away fromthe observer. At one side of the throat portion 2 there is provided afeed plate 3 of conventional type having the usual openings (not shown)through which a feed dog member A is adapted to move.

Located in the entering portion of the throat portion 2, We provide apresser foot 5 of more or less conventional shape opposing and adjacentto the feed plate 3, and mounted upon a support indicated generally at 6in such manner as to be adjustably spaced from the feed plate 3. Thesupporting means for the presser foot 5 indicated generally at 6 isconstructed according to any well known manner to exert a flexiblebiasing force normal to the face of the feed plate 3. Thus the presserfoot 5 may be adjusted to clear the feed plate 3 by a distancecommensurate with the thickness of the material being sewn, whileyieldably resisting further displacement from the feed plate 3.by aforce commensurate with the extent to which the material being sewn mustbe gripped by the feed dog 4 and the presser foot 5 at each period ofadvancement. It will be understood that the requiredgripping force mayvary considerably but that, in sewing the mouths of previously filledheavy paper bags of large capacity, this force will be far more severethan is required in machines to be employed for lighter duty as, forexample, for the sewing of relatively small cloth bags. The specificmechanism for applying this yielding bias force to the presser foot 5 issimilar in principle to that employed in previous machines and here neednot be described in de tail.

In the instance illustrated, the sewing machinel is provided with a maindrive shaft Hi journalled in bearings l l and I2 attached to or forminga part of the frame 9, which drive shaft if! has a principal axisperpendicular to the plane of the material being sewn and is providedwith driving pulleys l3 and it and a hand wheel 55,

r all of which are conventional in character and have no bearing uponthe present invention except insofar as they typify means whereby theshaft it} may be connected to a suitable driving motor (not shown). Atone end of the shaft ill, there is provided an eccentric or crank memberit which is operatively connected by means of a connecting rod ill to abell crank it pivotally mounted upon a pin l9 attached to the frame I.The end of the bell crank 18 opposite to that pivotally connected to therod H is operatively connected by means of a link or links 2! to a lug22 mounted upon a needle holder bar 23 having a needle 2% and iournalledin bearings 25 mounted upon and forming a part of the frame 1.

The principal axis of the needle bar 23 is normal to the face of thefeed plate 3, that is to say, normal to the plane of the material beingsewn, and parallel to the principal axis of shaft l8 and in eachrevolution of the shaft it, the needle bar 23 is caused to move forward,thrusting the needle through the material being sewn and the openings inthe presser foot 5 and the feed plate 3 into the position in which it isillustrated in Figs, 1 and 2 and then to be withdrawn from the materialbeing sewn in order to permit the material to be moved ahead withrespect to the needle by the feed dog 4% in a position for the nextstitch.

The needle 2 is provided with the usual eye (not shown) through whichpasses the needle thread 35. The latter is supplied to the needle 2%from a suitable thread stand (not shown) through a thread tension deviceH, a guide tube 32, an eye 33 mounted upon the rear end of the needlebar 23 and fixed eyes 3 5 conventionally located adjacent the bearings25.

In the present instance, the reciprocation of the needle 2% carrying thethread 33 cooperates with a looper 35 carrying a second thread 35 toform a double-thread interlocked chain stitch. The looper 35 is fullyillustrated except for its extreme tip in Fig. 1. For a betterunderstanding of the lcoper and of the type of stitch for ned by themachine reference may be made to the United States Patent of GeorgeHoepner #1270948, i..- sued July 2, 1918, wherein is illustrated andclaimed a single form of the same general type of looper. The looper 35is mounted in a holder arm 3'5 attached to one end of a rod the otherend of which is pivotally attached to an eccentric portion 39 of themain drive shaft it. The rod is slidably mounted in a sleeve member itpivotal- 1y mounted at H to the frame l. A part of sleeve member dii isremoved in Fig. 5 for the sake of clarity.

It will be understood by those skilled in the art and familiar withdevices of this character that, as the shaft it rotates, the looper 5. 5is caused to travel in a closed and more or less narrow elliptical pathlying in a plane parallel to the plane of the material being sewn,during the course of which path it passes downward on one side of thethen retreating needle and enters a loop being formed in the needlethread 363, and subsequently rises on the other side of the path of theneedle, producing atriangle of thread, one side of which is formed bythe aforesaid locper, another side by the looper thread 36, and the thirby the aforementioned loop, which triangle is entered by the nee die onits next forward motion. Shortly thereafter, the loop is stripped fromthe rising looper, thereby producing an interlocking of the needlethread 3!) and the looper thread 3% on one side of the material beingsewn.

Our improved mechanism for feeding the rial to be sewn through themachine, or for advancing the sewing machine relative to ".13 materialbeing sewn, as the case may be, between the stitching intervals, is bestillustrated in Figs. 3, i and 5 to which reference will now be had. Thefeed dog t, as mentioned hereinabov-e, is required to periodicallyadvance through the throat plate 3 to grip the material against thebiased presser foot 5, then to move forward in the direction of movementof the material being sewn relative to the sewing machine while grippingthe material,

then to be retracted out of engagement of the material being sewnthrough the throat plate 3 and finally to move back in a directionopposite to the direction of the material being sewn with respect to thesewing machine in order to complete its cycle and to be ready to beagain advanced to grip and move the material being sewn.

In order to provide for this motion of the feed dog 4 and to insure thatthe forward motion of the feed dog, while in engagement with thematerial being sewn, will be in a substantially straight line ratherthan in v curved or arcuate line, the feed dog 4 is mounted upon an armor feed dog holder 50, the opposite end of which terminates in a sleeve51 mounted upon a pin 52 secured to the frame I at a suitable distancefrom the throat plate 3 and extending parallel to the stitching line,that is to say, parallel to the direction of movement of material beingsewn with respect to the sewing machine. The sleeve 5! is so mountedupon the pin 52 as to be capable of a sliding movement along the pin 52or a rocking movement about the latter. The pin 52 may be provided withan enlarged head 53 to limit the movement of the sleeve 5! along thesame. In order to provide for the forward and backward sliding movementof the sleeve 55 along the pin 52, the arm 56 is provided with a stud 54which is adapted to be received into and freely held by the bifurcatedend, or, preferably, within an oval hole through a member 55 mounted inthe end, of a rocking lever 56 pivotally mounted at 5'! on a supportingmember 58 attached to the frame I and having at its opposite end a yoke6| adapted to receive an eccentric 62. The eccentric 62 is mounted uponthe main drive shaft l6, and as the shaft it! rotates the eccentric 62swings the rocking lever 56 to and fro about the pivot 51 and throughthe stud 54 causes the arm 50 to slide to and fro along the pin 52.

The manner in which the stud 54 connects arm 50 to lever 56 is such thatthe arm 50 is free to rock slightly about the pin 52 withoutinterferingwith the motion imparted by the rocking lever 56 and the eccentric 62.

We further provide a spring or springs 63 lying between the arm 56 andthe rocking arm 56, which springs 63 exert a biasing force tending torock the arm 59 about the pin 52 in a counter-clockwise direction asviewed in Fig. 5 and thus keeps the feed dog 4 retracted out ofengagement with the material being sewn and member 64 against cam member65 as will appear hereafter.

In order to provide for advancing and retracting the feed dog 4 throughthe openings in the throat plate 3, the arm 56 is provided with arearwardly extending member 64 preferably connected to the arm 56immediately behind and adjacent to that point at which the materialreceives the thrust of presser foot 5. It will be obvious, however, thatthe member 64 may readily be attached to the feed dog 4 if so desiredbut, in any event, the member 64 is preferably so situated as to bedirectly aligned with the force exerted by the flexibly biased presserfoot 5 when the feed dog 4 is in its advanced position in engagementwith the presser foot 5 or the material being sewn.

Lying immediately behind the member 64 and limiting rearward motion ofthe member 64 and the feed dog 4 under the influence of the spring 63 weprovide a sliding cam member 65, the rear face of which opposite themember 64 is provided with an inclined salient cam portion 66. which'lies adjacent to and, upon vertical reciprocation of the member 65 isadapted periodically to engage and ride over an'inclined salient camportion 61' of a fixed canr member 68 which may convenient 1y beattached to the frame I. Preferably, the

inclined cam portion 61 is provided on a separable and adjustablymounted part 69 which is simple to make and negligible in cost. It willbe obvious that, upon vertical downward movement of cam I member 65, camsurfaces 66 and 61 will slide past each other and cause a resultanthorizontal movement of the cam member, thereby causing the feed dog tomove outwardly. This motion of the feed dog is accomplished throughtransmission of the outward thrust by member 64 to cause theswinging ofarm 50 about pin 52. Upon upward movement of cam member 65, the camsurfaces will disengage and the feed dog will be retracted due to thethrust of the presser foot, this motion being furthered by springs 63 toinsure complete retraction of the feed dog below the surface of throatplate 3. Cam member 65 is guided in its reciprocatory movements betweenthe frame I and a flange 10 on member 68.

In order to providefor vertically reciprocating the member 65 in suchtimed relation with respect,

to the oscillation of the rocking member 56 as to alternate the periodsof maximum rates of advancement and retraction, respectively, of thefeed dog 4 through the throat plate 3 with the forward and backwardmotions, respectively, of the feed dog 4 in and against the direction ofmovement of the material being sewn, the member 65 is preferablyactuated by some form of eccentric mounted upon the shaft I0 and havinga predetermined angular position with respect to the eccentric 62 andthe rotation of the shaft l0. While a separate eccentric may be employedfor this purpose or the vertical reciprocation of the cam member 65 maybe derived from the eccentric 62 itself, in the present instance we haveillustrated a convenient and space-saving mechanism for effecting thevertical reciprocation of the member 65.

In this instance, the upper portion of the member. 65 is pivotallyconnected by means of a connecting rod H to a knuckle member 12 mountedupon the connecting rod 38 which actuates the looper 35 and, as theshaft l0 rotates, the knuckle 12 through the connecting rod H causes themember 65 to slide up and down thus alternately advancing and retractingthe feed dog 4 through the openings in the throat plate 3 in the mannerset forth hereinabove.

Knuckle 12 has an orbital movement in the plane of Fig. 4 and member 65has a. straight line movement in this plane, while knuckle 12 hasstraight line movement in the plane of Fig. 5 and joint 13 has anorbital component of movement in this plane due to the coaction of camsurfaces 66 and 61. Therefore. the joints at 12 and 13 each comprises auniversal joint to an extent sufiicient to allow for such movements.

It will be obvious from inspection of the draw ings and moreparticularly Fig. 5, that the force exerted by the presser foot againstthe feed dog 4 when the latter is advanced through the throat plate 3isresisted by the compressive strength of the members 64, 65 and 68 andthat the stress thus set up is substantially directly in alignment withthe direction of the force exerted by the presser foot 5. Due to thefact that the stress thus set up is resisted substantially entirely incompression and bending or shear stress is substantially and entirelyavoided, it is possible to construct the various parts receiving thestress much more lightly with respect to a given force :5

exerted by the presser-foot mechanism than would otherwise be true, and,consequently, it is possible according to our invention to greatlyreduce the inertia and weight of the feed-dog actuating mechanism ascompared with prior devices. This is especially important with respectto such relatively heavy presser foot action as is required to gripmaterials such as paper and more particularly the mouths of heavy paperbags.

Figs. 6, '7 and 8 are motion studies of the various. operating parts ofour sewing machine, which taken in connection with Figs. 3, 4 and 5 willeX-- plain the operation thereof. Figs. 4 and 5 are views taken at whatmay be termed the beginning of a working cycle, or of rotation of shafti0. Accordingly, Fig. 3 is taken at 90 of rotation. It is apparent thatas shaft Ill rotates 90 from the position of Fig. 5 to the position ofFig. 3, member 50 will move to the right approximately one half of itstravel, while cam member 55 moves downward in a straight line as camsurfaces 65 and 6'! approach each other. As a result the feed dog willhave a straight line movement to the right (Fig. 6). During this timelooper 555 (Fig. 8) descends approximately one half of its travel whileswinging to the left of the needle 2 which is then moving outward (Fig.7). During the next 30 of rotation cam surface 00 rides upon cam surface6'! while member 50 starts toward the left, causing the feed dog to bethrust forward along a curved path to engage the material.Simultaneously needle 24 clears the material. During the next 60 ofrotation cam plate 65 is traveling downward in a straight line whilemember 50 continues to move toward the left in a straight line, the feeddog gripping the material and feeding it through the machine.Simultaneously therewith, looper 35 travels to its lowest point whileswinging back toward. the right, but being still to the left of avertical plane through the needle line and below the needle. The next 60of rotation causes the feed dog to complete its working stroke, andduring the next 30 of rotation to retract as cam surface 6% slides offof cam surface 61. During this latter 90 of rotation the looper 35travels upward while swinging to the right of the needle, and during thelast 30 thereof the needle penetrates the material. The final 90 ofrotation causes the feed dog to return in a straight line to its initialposition, while the looper completes its orbital movement and the needlefully penetrates.

It is obvious from the foregoing that slight variations in theangularity of eccentrics will cause variations in the path relationshipof the various parts. Also, a vertical adjustment of member 69 may beutilized to create a longer or shorter working stroke of the feed dog.It is equally apparent that by changing the slope of the cam surfaces 60and 61 a quicker or slower outward movement of the feed dog may berealized. For example, in Fig. 9, the angle of slope of the cam surfaceshas been materially lessened so that 60 of rotation is required to causethem to pass each other, resulting in a short feeding stroke lastingonly 60 of rotation and allowing a greater proportionate period for theneedle to remain retracted in the material. In Fig. 10, the member 69has not been altered but has been lowered so that the feed dog remainsfor 10 more than in Fig. 6 before starting outward. This results in aworking stroke lasting only 100, as compared to 120 in Fig. 6. Manyother possible relationships may be evolved to meet immediate demands.However, the characteristics of the machine outlined in Figs. 6, 7 and8, have been found satisfactory and permissive of the followingdesirable features of operation, i. e., due to the fact that the feed.dog is operative only during 120 of rotation, the needle and looper areallowed 240 in which to form the interlocked chain stitch.

Obviously this allows a substantially greater number of stitches perminute and a correspondingly higher output of bags.

In the foregoing, it is made clear that the feed dog is imparted astraight working stroke shorter than the full reciprocation of member.50 along pin and during less than 180 of rotation of the shaft, or lessthan Pi radians. This allows a greater proportionate period for theneedle and looper to cooperatively interlock the threads and hence agreater number of stitches per minute. It also clear that by adjustmentof member 69,

operative angle of rotation is lessened commensurately with lessening ofthe straight line working stroke, so that adjustments in the length ofstitch is made possible.

Another feature of our invention is that the feed dog is mounted on'member 50 swinging about and slidable on pin 52. Thus the feed dog isrockably mounted on an axis'of rotation parallel to the plane of thematerial. The same effect would be obtained if the member 50 were formedwith pintles rotatably and slidably guided in holes in the walls of theframe 1, the important thing being that at the axis of the member 52, orits equivalent, thefeed dog holder may be considered as beingdisplaceable only in the line of the axis, while the opposite end of theholder and the feed dog are displaceable in two directions resolved intoa closed path of definite form and dimensions. The feed dog has only anegligible outward swing from the moment it contacts the material untilit reaches its full outward position, and the lift of the feed dog dueto its swinging movement is infinitesimal. The feed dog therefore may beconsidered as having a practically straight outward thrust and does notdraw across and chew the material as was the case in the old machineshaving feed dogs mounted on long members swinging about a distant pivot.In other words, the feed dog while in contact with the material does nothave any motion or lateral displacement up or down from the line ofstitching.

As previously pointed out it is immaterial to the operation of ourdevice whether the material is drawn through the machine or the machinedrawn past the material as set forth in the aforementioned applicationsof Lincoln A. Cundall and Robert N. Cundall. The foregoing descriptionsets forth a stationary machine in which the feed dog i actually forcesthe material forward during the time the needle is withdrawn. However,our invention makes practical the use of continuous feeding of filledbags by causing the feed dog to positively grip the material and swingthe sewing head back after having been rocked forward by the engagementof the needle therewith, or the use of a sewing head which travels pasta. stationary bag by causing the feed dog to positively grip thematerial and pull the sewing head relatively thereto while the needle isdisengaged.

It will be obvious to those skilled in the art that while we have showna preferred form of mechanism whereby this result may be achieved, ourinvention is not limited in its broadest aspect to such specificembodiment but may variously be embodied within the scope of ourinvention, and

, other specific feed mechanisms of the general relatively stiifmaterials such as paper, cardboard, or the like, these advantages inpart consisting of improvements in the motion characteristics of themechanism as well as the structure of the mechanism itself.

As pointed out hereinabove, our invention is not limited to theparticular exemplification given hereinabove but may variously beembodied and utilized within the scope of the claims hereinafter made.

We claim:

1. In a sewing machine, a feed dog for advancing the material to be sewnin a series of intermittent movements relative to said machine, aholder, upon which said feed dog is mounted,

adapted to be reciprocated along a fixed axis extending parallel to thedirection of movement of the material relative to the sewing machine,and a fixed pin pivotally supporting said holder and constituting saidaxis, said holder having a length from said axis to said feed dog atleast several times the length of the arc of movement of said feed dogabout said axis.

2. In a sewing machine, a feed dog for advancing the material to be sewnin a series of intermittent movements relative to said machine, a

said feed dog about said axis toward and away j from the material, saidholder having a length from said axis to said feed dog at least severaltimes the length of the arc of movement of said feed dog when rocked bysaid means.

3. 'In a'sewing machine, a throat plate having openings therein, apresser foot located adjacent to said throat plate and flexibly biasedtoward said throat plate, a feed dog adapted to be advanced through theopenings in said throat plate to grip the material being sewn againstsaid presser foot and to be withdrawn through said openings and out ofengagement with said material, a holder upon which said feed dog is-vmounted, a pin having its principal axis located in a plane parallel tothe face of said throat plate and pivotally supporting said holder, saidholder having a length from said axis to said feed dog at least severaltimes the length of the arc of movement of said feed dog to engage thematerial, means for rocking said holderabout said pin to advance andretract said feed dog through said throat plate, said means comprisingmembers located substantially in line with said feed dog and saidpresser foot and constituting a rigid backing for said feed dog, andmeans to move said holder along said pin to cause said feed dog toadvance the material engaged thereby with respect to said throat plate.

HOWLAND F. BRIGGS. ROBERT N. CUNDALL.

